The effect of Pt surface orientation on the oscillatory electro-oxidation of glycerol

Abstract

• The anion (bi)sulfate of the electrolyte exerts a strong influence on the electro-oxidation of glycerol on basal and stepped Pt single crystal surfaces. • Cyclic voltammetry reveals that when there is an increase in sulfate concentration, the glycerol oxidation current density decreases. • Chronoamperometric studies showed that Pt(110) and stepped surfaces exhibited greater ability to catalyze the glycerol electro-oxidation than Pt(111). • Emergence of potential oscillations obtained during glycerol oxidation over Pt( hkl ) and stepped surfaces highlights different mechanisms of the reaction. In the present paper, we have studied the influence of (bi)sulfate anion (0.1 and 0.5 M) on the electro-oxidation of glycerol on basal Pt( hkl ) and stepped surfaces belonging to the series of Pt(S)[ n (111) x (111)]. Cyclic voltammograms and derivative voltammetry pointed out that the catalytic activity decreases for Pt(111) and Pt(110) and, to a minor extent, for stepped surfaces in 0.5 mol L -1 H 2 SO 4. Chronoamperometric curves demonstrated that above 0.60 V ( vs. RHE), for both concentrations (0.1 and 0.5 mol L -1 H 2 SO 4 ), stepped surfaces and Pt(110) showed greater ability to catalyze the glycerol electro-oxidation in comparison with Pt(111). Potential oscillations were mapped along with slow galvanodynamic sweeps and studied at constant current. For Pt(111), no oscillations were found in the galvanodynamic regime, however, under the galvanostatic regime, period 1 oscillations were observed after a long induction period. The oscillations showed a very similar profile for stepped surfaces, even for the Pt(332) surface, which has a high density of (110) steps. Pattern changes were observed only for Pt(110) compared to other surfaces. Therefore, we conclude that (110) step sites influence the oscillatory behavior, thus the insertion of the steps favors the path of formation of inactive species, which compete for the same catalytic sites in a given potential region. The extinction of the mechanism oscillatory occurs differently due to the intrinsic characteristics of each surface electrode for the formation of (hydro)oxides.